[Info-ingres] question about READ UNCOMMITTED

[Roy Hann]

Paul White wrote:

> I read something interesting about READ UNCOMMITTED and NOLOCK in MSSQL.
>
> Along with the expected Dirty Reads, Non-Repeatable Reads, and Phantom
> Reads, there is something called "Same Data is Read Twice".  
>
> This page describes the MSSQL feature.
> http://sqlblog.com/blogs/tamarick_hill/archive/2013/05/06/pros-cons-of-using
> -read-uncommitted-and-nolock.aspx
>
> Apparently it is possible to duplicate records from a simple join from
> several tables with unique primary keys.
> Does Ingres have this feature :-)

I assume you use a smiley there to signal your ironic use of the word
"feature".

I don't know that I've ever observed duplicate reads happening Ingres,
but I don't know of any reason why it wouldn't happen if you 
subvert the consistency controls by turning off locking.

As a general rule I expect any application that uses
READLOCK=NOLOCK to produce all kinds of insane shit, and not to be
taken seriously. I have been ranting--right here--against using
READLOCK=NOLOCK for decades.

Roy